package network;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

/*
 * @author zzr
 * @date: 2025/04/18  16:21
 * @description: UDP 回显服务器实现~
 */
public class UdpEchoServer {

    private DatagramSocket socket = null;

    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("启动，服务器！");
        // 每次循环，就是处理一个请求 - 解析的过程
        while (true) {
            // 1. 读取请求并且解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096], 4096);
            socket.receive(requestPacket);
            // 将读到的字节数组，转换成 String 方便后续的逻辑操作
            String request = new String(requestPacket.getData(), 0, requestPacket.getLength());

            // 2. 根据请求计算响应（对于回显服务器来说，这一步什么都不需要做）
            String response = process(request);

            // 3. 把响应返回给客户端

            // 构造一个 DatagramPacket 作为响应对象
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),
                    response.getBytes().length, requestPacket.getSocketAddress());
            socket.send(responsePacket);

            // 打印日志
            System.out.printf("[%s:%d] request: %s , response: %s \n",requestPacket.getAddress().toString(),
                    requestPacket.getPort(), request, response);
        }
    }

    public String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(9090);
        server.start();
    }
}
